Service providers offering virtual private network (VPN) services (e.g., Layer 3 or Layer 2) over Border Gateway Protocol are expected to have multiple paths (e.g., equal cost multi-path or “ECMP”) between ingress provider edge (PE) routers and egress PE routers that are commonly provisioned with VPN services. In such scenarios, any intermediate/transit node with multiple (e.g., ECMP) paths to an egress PE can use some selected information as input for hashing in order to decide the egress interface for packet forwarding. For example, this information can be either L3/L4 details from the packet, Entropy Labels, or 3/5/7-tuple entities.
Notably, however, if one of the multiple paths (e.g., label-switched paths or “LSPs”) is broken due to reasons such as hardware programming corruption, label mismatching, encapsulation protocol being broken, etc., then any traffic forwarded on that failed path would get dropped or black-holed, even if all other paths are healthy. This is because the node performing the ECMP action may not be aware of the path failure elsewhere.